How to turn a mint into catmint: the origins of specialised metabolism

由于植物不能移动，它们必须找到创新的方式来保护自己并与环境相互作用。许多植物提出的解决方案是制造具有特定功能的独特化学物质，例如驱除昆虫或提供太阳紫外线的保护。这些化学物质中的许多被称为天然产物，被人类用于香料和药物。了解植物是如何进化成这些化学物质的，将有助于我们了解植物如何适应环境的核心方面。它也可能为我们将来如何制造类似天然产物的化学品提供经验。我们正在研究植物如何进化以制造新的化学品。我们的研究重点是猫薄荷，也被称为猫薄荷或荆芥。猫薄荷以其对猫的欣快作用而闻名，这是猫薄荷产生的一种叫做荆芥内酯的化学物质的结果。猫薄荷是薄荷家族的一员，薄荷家族包括熏衣草、牛至，当然还有薄荷。然而，猫薄荷已经在薄荷中独特地进化成了荆芥内酯。我们将试图找出薄荷是如何进化成猫薄荷的：荆芥是如何进化成这种独特的化合物的？为了研究这一点，我们将首先获得不同猫薄荷物种和近亲的基因组序列。基因组序列本质上是生物体基因的集合，通常被认为是生物体的DNA“蓝图”或一组指令。基因组将向我们展示不同物种中参与合成荆芥内酯的基因，我们还可以看到基因在基因组中的相对位置。我们可以通过计算，推算出几百万年前猫薄荷祖先的基因是什么样子的。“这让我们可以在实验室里复活和测试这些古老的基因，看看猫薄荷的祖先可以制造什么化学物质。一旦我们有足够的基因组进行良好的和可靠的分析，我们将专注于NEPS基因，负责制造荆芥内酯。”这些基因在猫薄荷的祖先身上发生了惊人的快速变化。我们将在猫薄荷进化史上的重要时间点复活这些古老的基因，并在实验室中测试它们，看看它们的行为如何改变。我们将观察它们从一个正常的基因转变为一个可以制造荆芥内酯的基因发生了什么变化。然而，植物需要许多基因来制造像荆芥内酯这样的化学物质，而不仅仅是一个。因此，我们必须将这种祖先分析扩展到多个基因，我们计划同时测试多种基因，以重建“祖先代谢”，从而确定猫薄荷的祖先可以制造哪些化学物质。我们还将试图找出基因在进化过程中在基因组中的位置。基因在进化过程中似乎会在基因组中跳跃，我们希望通过比较基因的行为和基因组位置来发现为什么会发生这种情况。进行所有这些研究将使我们能够回答猫薄荷何时以及如何获得制造荆芥内酯的能力。反过来，这将为植物如何制造新的化学物质以及它们的基因和基因组如何进化以适应环境提供更广泛的经验教训。植物是自然界的绿色化学家：了解植物如何制造有用的化学物质可以帮助我们以环保的方式制造我们自己的植物灵感化学品。

As they cannot move, plants must find innovative ways to defend themselves and interact with their environment. The solution that many plants have come up with is to make unique chemicals with a particular function, such as repelling insects or providing protection from the sun's UV rays. Many of these chemicals, known as natural products, are used by humankind for fragrances and medicines. Finding out how plants have evolved to make these chemicals will help us understand a core aspect of how plants adapt to the environment. It may also provide us with lessons for how to make similar natural product-like chemicals in the future.We are investigating how plants evolve to make new chemicals. Our research focuses on catmint, also known as catnip or Nepeta. Catmint is famous for its euphoric effects on cats, which is the result of a chemical produced by catmint called nepetalactone. Catmint is part of the mint family, which includes plants such as lavender, oregano and, of course, mint. However, catmint has evolved uniquely amongst the mints to make nepetalactone. We will try to find out exactly how a mint has evolved into catmint: how did Nepeta evolve to make this unique compound?To investigate this we will first obtain genome sequences of different catmint species and close relatives. A genome sequence is essentially a collection of an organism's genes, and is often considered a DNA "blueprint" or a set of instructions for an organism. The genomes will show us the genes that are involved making nepetalactone in the different species, and we can also see how genes are positioned on the genome relative to each other. We can perform calculations to estimate what the genes of catmint ancestors looked like many millions of years ago. This allows us to resurrect and test these ancient genes in the lab to find out what chemicals the ancestors of catmint could make.Once we have enough genomes to perform good and robust analyses, we will focus on genes called NEPS that are responsible for making nepetalactone. These genes went through remarkable rapid changes in the ancestor of catmint. We will resurrect these ancient genes at important time points in catmint evolutionary history and test them in the lab to see how their behaviour has changed. We will be looking out for what changes occurred for them to transform from a normal gene to one that can make nepetalactone.However, plants need many genes to make chemicals like nepetalactone, not just one. We must therefore extend this ancestral analysis to multiple genes, and we plan to test a variety of genes simultaneously to recreate an "ancestral metabolism" and so determine what chemicals the ancestors of catmint could make. We will also try to work out where in the genomes the genes were positioned during evolution. Genes appear to jump around in genomes as they evolve and we hope to discover why that happens by comparing the gene's behaviours with the genome locations.Conducting all of this research will allow us to answer when and how catmint gained the ability to make nepetalactone. This, in turn, will provide wider lessons for how plants make new chemicals and how their genes and genome evolve to adapt to the environment. Plants are nature's green chemists: learning how plants make useful chemicals could help us to make our own plant-inspired chemicals in an environmentally friendly manner.